from itertools import accumulate

n = int(input())
counts = [0] * (n + 1)
for i in range(1, n + 1):
    for j in range(i, n + 1, i):
        counts[j] += 1
ans = 0

accu = [0] + list(accumulate(counts))
for i in range(n + 1):
    ans += counts[i] * (accu[n - i + 1] - accu[1])
print(ans)
